Wind power is considered one of the cleanest, most environmentally friendly energy sources presently available, and wind turbines have gained increased attention in this regard. A modern wind turbine typically includes a tower, a generator, a gearbox, a nacelle, and one or more rotor blades. The rotor blades capture kinetic energy from wind using known airfoil principles and transmit the kinetic energy through rotational energy to turn a shaft coupling the rotor blades to a gearbox, or if a gearbox is not used, directly to the generator. The generator then converts the mechanical energy to electrical energy that may be deployed to a utility grid.
To ensure that wind power remains a viable energy source, efforts have been made to increase energy outputs by modifying the size and capacity of wind turbines. One such modification has been to increase the length of the rotor blades. However, as is generally understood, the loading on a rotor blade is a function of blade length, along with wind speed and turbine operating states. Thus, longer rotor blades may be subject to increased loading, particularly when a wind turbine is operating in high-speed wind conditions.
During the operation of a wind turbine, the loads acting on a rotor blade are transmitted through the blade and into the blade root. Thereafter, the loads are transmitted through a pitch bearing disposed at the interface between the rotor blade and the wind turbine hub. Typically, the hub has a much higher stiffness than the rotor blades. Thus, due to the varying (or non-homogeneous) stiffness, the loads are often not evenly distributed around the pitch bearing. As a result, the unequal load distribution may create areas of high loading in the pitch bearing, thereby resulting in higher stress and/or damage to the pitch bearing. For example, in certain embodiments, the pitch bearings may have a relatively large diameter (e.g. approximately 2 meters) and as the loads on the outer race vary over its surface, the outer race may acquire a shape similar to that of a potato chip (i.e. the potato chip effect).
Accordingly, the art is continuously seeking new and improved pitch assemblies that provide a more even load distribution so as to reduce the localized stress within the pitch bearing.